The primary mission of the power utility is to deliver power to consumers reliably and cost-effectively. Ultimately, consumers do not care about the intricacies of managing power systems, but they require that the system “works.” For the average consumer, whether a power system works or not depends largely on the design of their devices, which can vary based on things like government legislation.
To that end, standards bodies closely regulate the power utility, specifying things like the nominal bus voltage, frequency and allowed range of variability. Collectively, the difference between these parameters and their nominal values is power quality.
Voltage, power factor, harmonics and managing transients are the important attributes of received power, and the utility must ensure that these are consistent even amidst disturbances in the line. One common disturbance that can often cause power system stability issues is lightning strikes, which cause a temporary surge in transmission line voltage. Since loads vary with time, the utility cannot guarantee power quality without designing resilient systems capable of dynamically varying with the needs of the system.
In the ideal situation, voltage should appear as a sinusoidal wave at exactly the mains voltage and frequency. The image below provides a graphical illustration of the four most common power quality issues that utilities must work to eliminate to the extent possible.
The cause, behaviour and effects of each of these will be the topic of future posts.
This article was taken from a report which I co-authored. It was submitted to ECE3333: Power Systems I, taught by Professor Rajiv Varma at the University of Western Ontario in Spring 2009.